Purpose :
To investigate the impact of dark adaptation time on scotopic retinal sensitivity thresholds, the test-retest repeatability of the scotopic microperimetry S-MAIA (CenterVue, Padova, Italy) and assess the possibility of a practice effect.

Methods :
Healthy individuals aged 18 years or older were invited to participate in two examination sessions. Exclusion criteria included diagnosis of any ocular disease, opaque ocular media, high refractive error +/-10D and history of squint. The eye with less refractive error was selected after an auto-refraction measurement (ACCUREF K-900, Shin-Nippon, Japan). In the first session, a microperimetry training (fast exam option) was performed under mesopic conditions (white stimuli) to familiarise with the testing concept. Participants then performed microperimetry under scotopic conditions with cyan (C) and red (R) stimuli after 10 minutes of dark adaptation (001lux/11m2), followed by a 10 minute break in mesopic illumination. This testing sequence was followed by 20 and 30 minutes of dark adaptation period with intervening breaks at the same visit. The second session included the same procedures excluding the “fast exam” session. Statistical analysis included production of Bland-Altman graphs, calculation of intra-class correlation coefficient, repeated measures ANOVA and one-way ANOVA.

Results :
Twenty-four individuals (mean age= 32.3 ± 10.5 years old) were recruited to this study. Four were excluded for inability to finish all tests. The 30 minute dark adaptation time on scotopic threshold was statistically significant against the 10 (<0.01) but not the 20 minutes (p=0.06). Bland-Altman plots showed that for both (C and R) stimuli tests, measurements were within the 95% confidence limits. Intra-class correlation coefficient was 0.90 for the C, 0.74 for the R and 0.86 for their difference (C-R) respectively. Finally, there was no evidence of a learning effect for the cyan (p=0.12), while there is some suggestion of a learning effect with the red test (p=0.05).

Conclusions :
The data suggest that a minimum dark adaptation time of 20 minutes is required to perform reliable and repeatable scotopic microperimetry. A significant learning effect was not observed.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.